CASC2D模型的降雨时间尺度效应影响

Effects of Rainfall Time Scale on CASC2D Model

水文模型是流域降雨-径流过程模拟的重要工具,基于物理机制的产流计算需考虑逐个计算单元的降雨强度和下渗强度关系,对降雨数据精度要求较高。以半干旱地区志丹流域降雨数据为研究对象,通过对最大降雨强度的时间尺度变化规律进行分析,基于自相似理论构建不均匀降雨差值方法,通过不同时间尺度的降雨输入研究CASC2D模型的时间尺度效应,结果表明:(1)降雨时间尺度的增加会明显削弱降雨分布不均匀特性,时间间隔越长,峰值降雨强度越小,降雨极值数越少;(2)在1~4h尺度内的最大降雨强度与时间间隔呈迅速减小的对数函数关系,在4~12 h尺度内的最大降雨强度与时间间隔呈缓慢减小的线性函数关系;(3)降雨时间尺度对CASC2D模型的产流参数和模拟精度具有明显影响,需要增大饱和水力传导度以保证模型的模拟精度。

Hydrological model is an essential tool for catchment rainfall-runoff simulation.Physically-based runoff calculation needs to consider the relationship between rainfall intensity and infiltration intensity of each calculation grid,which requires high accuracy of rainfall data.Based on the analysis of rainfall data in Zhidan catchment,which is a semi-arid catchment,the time scale variation of maximum rainfall intensity is studied.Based on the self-similarity theory,the method of uneven rainfall disaggregation was constructed.The time scale effect is studied by using the different time scales of rainfall input in CASC2D model.The results show that,(1)the increase of rainfall time scale will obviously weaken the uneven distribution characteristics of rainfall,with the longer time interval,the smaller peak rainfall intensity and the fewer rainfall extreme value;(2)the maximum rainfall intensity in the time scale of 1-4 h decreases rapidly as a logarithmic function with the time interval,and the maximum rainfall intensity in the time scale of 4-12h decreases slowly as a liner function with the time interval;(3)rainfall time scale has significant impact on the runoff generation parameters and simulation accuracy of CASC2D model,which need to increase the saturated hydraulic conductivity to ensure the simulation accuracy of the model.